Cementitious compositions and aggregate derivatives from said compositions

ABSTRACT

Cementitious compositions and aggregate derivatives of said compositions wherein fluidized bed combustion residue and pozzolanic material, such as pulverized coal combustion system fly ash, are incorporated in a cementitious mix. The mix is cast into desired shape and cured. If desired, the shape may then be crushed so as to result in a fluidized bed combustion residue-fly ash aggregate material or the shape may be used by itself.

This is a division of application Ser. No. 50,206, filed June 20, 1979, U.S. Pat. No. 4,250,134.

FIELD OF THE INVENTION

The present invention relates to a novel cementitious compositions comprising the spent residue from a fluidized combustion bed of the type wherein lime or limestone particles are suspended in a fluidized medium, and wherein a carbonacoues fuel is ignited proximate said fluidized medium to capture therein substantial amounts of sulfur oxide impurities which are generated upon ignition of the carbonaceous fuel. The invention further relates to aggregate derivatives of said cementitious compositions and to a method for producing both the aggregate and cementitious composition itself. The cementitious compositions produced in accordance with the invention exhibit extremely high compressive strengths so as to allow their use in load bearing applications. The aggregates produced in accordance with the invention not only exhibit high compressive strengths, but are also able to withstand high shear abrasive forces so that the aggregates may successfully be substituted for conventional natural aggregates in most end use applications.

BACKGROUND OF THE INVENTION

The use of coal as a fuel in electric generator plants is well known. In recent times, emphasis upon the burning of coal for this purpose has been increasing due to the dependence of this country on foreign sources of oil, the relative scarcity of oil, and the high price thereof.

As the emphasis has shifted to the use of coal fuel, considerable opposition to its use, especially to the use of "high sulfur" cement fuel has steadily increased. Opponents of the use of coal rely upon the deletrious effects that SO_(x) emission (resulting from the combustion of coal) into the atmosphere have on the environment.

Generally, two approaches have been used to counter the problem of excess SO_(x) emissions. The first has been to provide elaborate off-gas scrubbing units in combination with the coal boiler or furnace in coal combustion systems, usually pulverized coal combustion systems. The more generally accepted systems utilize lime or limestone as preferred sorbents. These devices wash the gas and absorb the sulfur oxides, producing a slurry or sludge that contains the sulfur oxide in the form of calcium sulfite and calcium sulfate. Some of the sorbent material that is currently in use contains other ingredients such as dolomitic lime and/or proprietary additives. Generally, the commercial applications are based on the use of either finely ground calcium carbonate (limestone) or a suspension of calcium hydroxide which is produced frm high calcium quick lime.

Another solution to the problem of excess SO_(x) emission in coal combustion systems has been to provide a fluidized combustion bed of lime or limestone in which the coal is ignited. Preferably, the coal is pulverized and also floats within this fluidized bed during the ignition thereof. The suspended lime or limestone particles thus capture substantial amounts of the oxidized sulfur content of the coal in the form of sulfates and sulfites. After the spent fluidized bed combustion residue has been removed from the coal boiler furnace, problems with respect to the disposal thereof have been presented due to the various governmental regulations pertaining to the protection of the environment, and, also due to the fact that the spent residue has heretofore been thought useful for very few practical applications.

In my paper entitled "Development of Potential Uses for the Residue for Fluidized Bed Combustion Processes", FE 2549-3, I have suggested that the fluidized bed combustion residue be used, inter alia, as a cementitious matrix in the production of road base material, as a sorbent in gas scrubbers, and as a means for stabilizing scrubber sludge when fly ash is added to a combination of the residue sludge.

In my paper entitled "Development of Potential Uses for the Residue from Fluidized Bed Combustion Processes", FE 2549-6, I have suggested, inter alia, that a wet "blunging" pretreatment of the fluidized bed combustion residue is useful as a means of liberating the lime component of the residue (thus providing a relatively inexpensive source of lime) and that the compressive strength of scrubber sludge may be increased by mixing of the residue, sludge, and fly ash in certain proportions.

Accordingly, despite the above noted means by which the spent residue from a fluidized bed combustion system may be utilized, there remains a need for a commercially acceptable disposal method for the spent bed residue.

Despite the above noted disclosure of road base material including said residue, there remains a need for a high strength concrete-like material which incorporates such residue.

Of further importance is the need for a stable aggregate material which can be incorporated into concrete and concrete-like compositions to impart increased strength and dimensional stability thereto.

These and other needs are met by the present invention which is hereinafter described in detail.

DETAILED DESCRIPTION OF THE INVENTION

As used in my invention, the term "fluidized bed combustion residue" (hereinafter FBCR) refers to the spent residue collected from a coal boiler or furnace wherein lime or limestone particles are floated in a fluidized medium proximate to the coal ignition located so as to remove certain SO_(x) impurities from the ignited coal, which coal is usually in the pulverized state. Fly ash, comprising finely divided siliceous-alumina glass compounds, usually accompanies the off gas through the flue and is removed by means of a bag house or the like.

The composition of the FBCR varies slightly from coal boiler location to coal boiler location. The physical properties of the fluidized bed combustion residue taken from a first boiler plant location are provided in Table 1.

    ______________________________________                                         PHYSICAL PROPERTIES                                                            ______________________________________                                         1. Gradation (range of all testing to date) - ASTM D 422 - 63                  Sieve Size   % Passing Sieve                                                   ______________________________________                                         3/8"         100                                                               #4           98.8-100.0                                                        #10          82.5-98.8                                                         #40          1.4-50.1                                                          #200         0.2-4.1                                                           ______________________________________                                         2. Compaction test - ASTM D 1557 - 70 - Modified Moisture                       Density Relationship                                                          Maximum dry density    109 pcf                                                 Optimum moisture content                                                                              15.7-18.9%                                              3. Dry rodded weight - ASTM C 29 - 77.1 pcf                                     Loose unit weight - ASTM C 29 - 72.4 pcf                                      4. Atterberg limits - ASTM D 423 - 66 and ASTM D 424 - 59                      Plastic limit       No plasticity                                              Liquid limit        34%                                                        Plastic index       Non-plastic                                                5. California bearing ratio - ASTM D 1883 - 73                                 Sample No.     1         2         3                                           ______________________________________                                         Dry density (before                                                            soaking)       91.6 pcf  94.0 pcf  89.3 pcf                                    Moisture content (initial)                                                                    13.4%     13.3%     12.9%                                       Moisture content (top 1"                                                       after test)    26.9%     25.9%     25.4%                                       Swell          0.029     0.035     0.031                                       Swell          0.41%     0.49%     0.44%                                       Bearing ratio                                                                  0.10 inch      105.0%    85%       48.3%                                       0.20 inch      106.7%    90%       66.7%                                       ______________________________________                                    

In certain cases, the fluidized bed combustion residue was preconditioned with sufficient water to hydrate the quick lime and release the heat of hydration prior to testing of the residue. The grain size analysis, dry rodded weight and loose weight determinations were performed on dry "as received" residue.

The general soil description of the fluidized bed combustion residue from the first plant location, based on the gradation and plasticity characteristics, is that of a uniformly graded sand. The ASSHTO designation is A-1-b. The Unified Soil Classification System ascribes the letter designation SP for a poorly graded sand. Due to the friable nature of the residue, the classification could shift to SM for a silty sand after compactor forces are applied during placement of the residue in a fill. The loose and dry rodded weight of the residue are somewhat lower in value than natural sand, but the direct shear and permeability data are more typical of a silty sand.

Table II indicates the chemical constituency of fluidized bed combustion residue taken from the first plant location.

                  TABLE II                                                         ______________________________________                                         RESULTS OF CHEMICAL ANALYSIS OF FBC RESIDUE                                    (FIRST PLANT LOCATION)                                                                        As Received                                                                             Milled FBC                                                            FBC Residue                                                                             Residue                                                               (%)      (%)                                                    ______________________________________                                         Loss on Ignition (LOI)                                                                          9.86       6.80                                               SiO.sub.2        11.60      12.30                                              CaO              55.82      56.92                                              Fe.sub.2 O.sub.3 4.70       3.66                                               Al.sub.2 O.sub.3 1.80       3.44                                               MgO              1.81       0.87                                               SO.sub.4         16.69      15.92                                              ______________________________________                                    

The "as received" residue from the first plant has an effective particle size diameter range of between 0.35-3.60 mm and an average particle size of 1.7 mm. The particle shapes of grains retained on a #30 mesh sieve are flat and angular. These characteristics are more pronounced as the particle size increases up to a #4 mesh material. The larger grains are flatter and subsequently sub-angular to a greater extent. The #8 mesh and larger material is reasonably sound and resistant to mechanical abrasion with finger pressure. Material passing through a #8 mesh sieve is readily friable, producing a light brown powder.

Coloration of the residue from the first plant on the whole is heterogeneous and varies from sample to sample but, in general, the plus #8 mesh material is uniformly reddish brown and similar to a red shell, while the intermediate particle sizes are brighter with a reddish hue speckled with black carbon and white particles. The fines are variable due to the lower percentage of fines available. They range from grey black to grey white in color. The particle size distribution of the "as received" FBCR and the resulting alteration by "milling" (crushed and ground in laboratory jaw crusher and pulverizer) are as shown in Table III.

                  TABLE III                                                        ______________________________________                                         Sieve Size  Approximate Percent Retained                                       ______________________________________                                         FBCR "AS RECEIVED"                                                             +4          2%                                                                 +8          8%                                                                 +16         52%                                                                +30         30%                                                                +60         7%                                                                 +100        2%                                                                 +200        1%                                                                 -200        Trace                                                              MILLED FBCR                                                                    +4          0%                                                                 +8          2%                                                                 +16         8%                                                                 +30         18%                                                                +60         60%                                                                +100        2%                                                                 +200        0%                                                                 -200        10%                                                                ______________________________________                                    

The net effect in milling the "as received" FBC residue was to fracture the average residue grain into six major parts, with one constituting a fine dust.

The specific gravity of the "as received" FBC residue from the first plant was slightly reduced on milling to possibly increase carbonation and anhydration of the exposed surfaces.

Other residue samples have been taken from the FBC boilers at two other plant locations. Table IV indicates the results of the chemical analysis of these additional two sample residues. Table V indicates the gradation of the two residues. Table VI indicates the results of X-ray diffraction analysis of the two residues.

In regard to the physical and chemical properties of the residue, during the combustion of the pulverized coal within the fluidized medium, the temperature of the fluidized bed causes the limestone particles to liberate carbon dioxide ##EQU1## without resulting in substantial diminution of the precursor limestone particle size. When the resulting quicklime component is subjected to the sulfur dioxide emanating from the combusted coal and to the molecular oxygen existing in the combustion air, an anhydrous calcium sulfate reaction product is formed by the following reaction: 2CaO+2SO₂ +O₂ →2CaSO₄. The CaSO₄ anhydrite is formed about the outer surface of the CaO particles and thus forms a shell which encapsulates the quicklime (CaO). The thickness of this shell is dictated by the length of exposure of the quicklime to the SO₂. If the CaO particle in the bed is small, the resulting reaction particle will be comprised of substantially all CaSO₄ anhydrite. On the other hand, and as is the case in most instances, the resulting reaction product will comprise spheres of anhydrous CaSO₄, with each sphere encapsulating a CaO (quicklime) core component. This factor distinguishes FBCR from other lime reaction products and provides a minor problem in that the CaSO₄ shells must be broken before the quicklime component of the residue can be liberated.

                  TABLE IV                                                         ______________________________________                                         CHEMICAL ANALYSES OF SECOND AND THIRD                                          PLANT LOCATION RESIDUES                                                               Second Plant Location                                                                        Third Plant Location                                             Residue (Samples                                                                             Residue (Samples                                                 Received 6/20/78)                                                                            Received 6/29/78)                                                Drum #1                                                                               Drum #2    Drum #1  Drum #2                                      ______________________________________                                         L.O.I.   15.54    15.54      0.94   0.66                                       SiO.sub.2                                                                               6.18     5.78       1.86   2.20                                       Al.sub.2 O.sub.3                                                                        4.13     3.96       1.22   2.04                                       Fe.sub.2 O.sub.3                                                                        8.37     7.84       4.18   3.66                                       CaO      47.74    51.42      63.53  59.49                                      MgO      7.06     7.75       2.03   3.22                                       SO.sub.4 11.94    11.96      26.73  29.04                                      ______________________________________                                    

                  TABLE V                                                          ______________________________________                                                       Approximate                                                      Sieve Size    Percent Passing                                                  ______________________________________                                         FBCR FROM SECOND PLANT LOCATION BOILER                                         200           78%                                                              100           92%                                                              60            96%                                                              40            98%                                                              20            100%                                                             FBCR FROM THIRD PLANT LOCATION BOILER                                          200            0%                                                              100            1%                                                              60             4%                                                              40            10%                                                              20            31%                                                              10            80%                                                              8             86%                                                              4             98%                                                              1/4           100%                                                             ______________________________________                                    

                  TABLE VI                                                         ______________________________________                                         X-RAY DIFFRACTION ANALYSIS OF THE                                              SECOND AND THIRD PLANT LOCATION RESIDUES                                                  Second Plant                                                                            Third Plant                                                ______________________________________                                         PEAK HEIGHTS (UNITS AT RANGE FACTOR 500)                                       CaSO.sub.4   80         136                                                    CaO          134        170                                                    CaCO.sub.3   30         --                                                     αSiO.sub.2                                                                            34         --                                                     COMPOSITIONAL RANGES                                                           CaSO.sub.4   Major      Major                                                  CaO          Major      Major                                                  CaCO.sub.3   Minor      --                                                     αSiO.sub.2                                                                            Minor      --                                                     ______________________________________                                          -- 1% or less                                                                  Trace <5%                                                                      Minor 5-25%                                                                    Major 25+%                                                               

In accordance with the invention, water is added to the FBCR in sufficient quantity to ensure hydration of all of the quicklime particles in the residue to calcium hydroxide. As above noted, the "as received" FBCR contains calcium sulfate anhydrate in the form of spheres which encapsulate the quicklime component, or substantially all of the quicklime component of the FBCR. Accordingly, in order to hydrate the quicklime component, a mixing or mechanical agitation of the residue is necessary. I have found that the addition of from about 20-30 weight % water to the FBCR is sufficient to hydrate substantially all of the quicklime of the residue. As may be seen from the above chemical analyses of the FBCR, the calcium oxide content thereof is usually on the order of about 50%. Of this 50% total approximately one-half is available as free lime. When hydrated, an approximate 16% weight increase in the material occurs due to the chemical combination of water. The addition of 20-30 weight % water to the FBCR provides excess water which may be lost due to evaporation caused by the heat given off during the hydration process.

Mixing of the FBCR and water for about 15 minutes ensures that the water necessary for hydration will come into intimate contact with substantially all of the free or available calcium oxide particles. Cooling of the residue to room temperature after mixing provides for safe handling, and also ensures that the hydration reaction is substantially complete.

Fly ash, or any other pozzolanic material comprised of various silico-alumino and iron compounds usually existing in the form of finely divided spherical glassy particles (as defined in ASTM Standard C-618) is then added to the FBCR water mixture within the range (based upon dry weights) of 10-90% fly ash or equivalent pozzolan to 90-10% of the residue.

Additional water may then be added to the mix to bring the moisture content of the mixture to within the range of about 9-20 weight %.

Cool boiler bottom ash, steel slag, or other natural aggregates may be added to the mixture, if desired.

The mixture is then compacted into the desired shape. In accordance with the invention, masonry blocks, bricks, rip rap, gabions, etc. may be formed from the FBCR-fly ash mixture.

The resulting shapes are then cured. The curing step may be carried out for a period of about 7-28 days or so in a temperature environment around 100 F. As is conventional in the art, steam may also be injected into the curing environment. Longer duration, and lower temperature curing environments may also be successfully utilized in accordance with the invention.

After the shape has been cured, it can be used for the intended application or it can be crushed, using conventional rock or stone handling or crushing equipment to form a desired end use aggregate. The thus formed aggregate may be readily stockpiled for long periods of time without excessive leaching or surface runoff which have normally characterized other stockpiled waste material. The aggregate may then be tested in accordance with the commercially used procedures for characterizing aggregates. As an example, ASTM standard Part 14 may be employed to ensure that the material can meet the requirements for various contemplated end use applications.

EXAMPLE 1

Cylindrical specimens (4" in diameter and 4.5" in height) were molded using mixtures representing 5 different ratios of FBCR and fly ash. The cylinders were compacted in accordance with the procedure specified in ASTM C-593 (three layers, 25 blows per layer, 10 lb. hammer dropped 18"). The resulting cylinders were cured for 7 days at 73° F., and then tested for compressive strength. The compressive strength, molding moisture content, and dry density of each sample are shown herein below in Table VII.

    ______________________________________                                         COMPRESSIVE STRENGTH OF MIXTURES                                               OF THIRD PLANT LOCATION FBC RESIDUE                                            AND PULVERIZED COAL FLY ASH                                                    Composition                                                                    Third Plant                                                                              Moisture                                                             Location  Content   Dry                                                        FBC    Fly    at Molding                                                                               Density                                                                               Compressive Strength                            Residue                                                                               Ash    (%)       (pcf)  (psi) @ 7 Days @ 73° F.                  ______________________________________                                         90%    10%    15.3      95.6   147                                                           22.1      98.3   274      233 Average                                          23.7      97.0   274                                             80%    20%    16.7      98.5   505                                                           19.4      104.8  410      408 Average                                          22.9      98.7   310                                             75%    25%    16.6      94.9   450                                                           20.2      99.1   540      433 Average                                          24.1      93.2   310                                             67%    33%    14.5      96.9   520                                                           18.9      102.0  760      617 Average                                          22.6      96.7   570                                             50%    50%    16.6      96.1   650                                                           17.7      97.3   930      807 Average                                          21.8      93.9   840                                             ______________________________________                                    

EXAMPLE 2

Reef blocks of FBCR and fly ash were molded and cured as indicated in Table VIII hereinbelow. As used herein, the term reef block is a structural unit which is used in the construction of an artificial reef which is adapted to act as a residence for certain organisms which are eaten by marine life. The blocks comprised 80% by weight based upon the dry weight of the mix FBCR and 20 weight % fly ash. The moisture content, dry unit weight and compressive strength of each of the samples is shown in Table VIII.

                  TABLE VIII                                                       ______________________________________                                         SUMMARY OF REEF BLOCK DATA                                                                                         Total Weight                                      Dry Unit Moisture Compressive                                                                               of Molded                                  Block  Weight*  Content* Strength* (psi)                                                                           Block                                      No.    (pcf)    (%)      7 Days at 100° F.                                                                  (lbs.)                                     ______________________________________                                         1      107.1    18.8     2590       104.2                                             114.1    15.8     2550                                                         116.3    13.5     2900                                                  2      113.1    14.0     1900                                                  3      113.3    14.6     2705       102.7                                             114.5    15.8     2270                                                         114.9    16.1     2310                                                  4      112.6    16.3     2470       104.0                                             112.0    15.2     2070                                                         112.1    15.2     1990                                                  5      114.4    15.8     2870       110.5                                             114.7    16.1     2870                                                         113.7    15.1     2030                                                  6      117.4    14.3     2670       103.8                                             113.1    16.8     2820                                                         113.7    14.5     N.T.                                                  7      117.8    14.8     2190       100.2                                             116.3    15.3     2590                                                         113.4    15.4     N.T.                                                  8      115.8    15.8     2030       102.0                                             114.0    14.6     2310                                                         115.2    16.2     1670                                                  9      106.1    19.1     1320       102.5                                             111.2    18.4     1340                                                         110.2    18.5      960                                                  10     N.T.     N.T.     N.T.       100.0                                             112.9     9.0     1670                                                         106.9    19.6     1750                                                  11     N.T.     N.T.     N.T.       106.0                                             109.4    15.7     N.A.                                                         106.1    16.0     N.A.                                                  12     N.T.     N.T.     N.T.       107.0                                             111.1    15.1     N.A.                                                         109.3    15.3     N.A.                                                  13     117.8    14.3     N.A.       107.0                                             114.0    14.9     N.A.                                                         115.0    15.5     N.A.                                                  Grand                                                                          Average                                                                               113.0    15.6     2194                                                  ______________________________________                                          N.A. -- Results not yet available                                              N.T. -- Not tested                                                             *Derived from compressive strength test cylinders.                       

Pellitized aggregate from FBCR-fly ash mixtures can also be made. In this case, pellet formation may be accomplished by means of either a pan or roll pelletizer.

EXAMPLE 3

Pelletized aggregate was made from varying FBCR-bituminous fly ash mixtures and from FBCR-FBC fly ash (top ash or flue ash in a fluidized bed combustion system). The pellets were produced by either roll pellitizing or pan pellitizing with moisture utilized as the binder in the roll pelletizing runs and with a sodium silicate solution being used for the pan pellitizer runs. The FBCR-fly ash proportions, mix additives and my remarks on the produced pellets are listed in Table IX hereinbelow.

                  TABLE IX                                                         ______________________________________                                         SUMMARY OF PELLETIZING TRIALS                                                            Pellet-                                                              Mixture   izing                                                                Percent   Tech-   Remarks                                                      by Weight nique   Mix Additive                                                                              Pellets                                           ______________________________________                                         50% FBC   Roll    22% Moisture                                                                              Good condition -                                  Residue   Pan     15% Sodium resisted moderate to                              50% Bituminous    Silicate Solu-                                                                            strong finger pressure,                           Fly Ash           tion       some surface dusting                              80% FBC   Roll    19% Moisture                                                                              Good condition -                                  Residue   Pan     15% Sodium resisted moderate to                              20% Bituminous    Silicate Solu-                                                                            strong finger pressure,                           Fly Ash           tion       more surface dusting                                                           than 50-60 pellets                                50% FBC   Roll    8% Moisture                                                                               Resisted moderate finger                          Residue                      pressure; easily abraded.                         50% FBC   Pan     15% Sodium Could not be pelletized.                          Fly Ash           Silicate Solu-                                                                 tion                                                         80% FBC   Roll    18% Moisture                                                                              Could not resist light                            Residue                      finger pressure                                   20% FBC   Pan     Sodium Sili-                                                                              Could not be pelletized.                          Fly Ash           cate Solution                                                                  of Varying                                                                     Strengths                                                    ______________________________________                                    

Sintered aggregate pellets comprising FBCR or combinations of FBCR and FBC fly ash can also be made in accordance with the invention.

EXAMPLE 4

Sintered pellets utilizing four size ranges of FBCR were investigated. The size ranges were: As received 100%-10 mesh, 100%-30 mesh, 100%-100 mesh. Small quantities of the pellets were formed by extruding compositions of either 100% FBCR or 80% FBCR blend with 20% FBC fly ash. In all cases, water was used as the binder, with the percentage of moisture addition ranging from 15% up to 40%, depending on the gradation and composition of the pellets.

"Green" pellets representing different size ranges, compositions and moisture content were heated in a muffle furnace manufactured by the Hevi Duty Electric Company, to the following temperatures: 1800° F., 2000° F., 2200° F., 2400° F. As herein used, the term "green" signifies unfired, freshly formed pellets. The pellets were tested for breaking strength while "green" and at the temperatures above noted. The results of this Example appear hereinbelow in Table X.

                                      TABLE X                                      __________________________________________________________________________     COMPRESSIVE STRENGTH OF SINTERED AGGREGATE PELLETS MADE FROM FBC RESIDUE       Pellet Formulation                                                             FBC             Moisture                                                                             Pellet Description                                       Residue                                                                             Fly Ash                                                                             FBCR  Content*                                                                             Green          Pellet Breaking Strength                                                       (pounds)****                              (%)  (%)  Gradation                                                                            (%)   Consistency                                                                           Green Texture                                                                          Green                                                                               1800° F.                                                                     2000° F.                                                                     2200° F.                                                                     2400°          __________________________________________________________________________                                                              F.                    100  --   As is 20    Good   Very rough                                                                             24   24   26   40   Melted                100  --   -10 mesh                                                                             15    Powdery                                                                               Rough   --   --   --   --   --                    100  --   -10 mesh                                                                             20    Rough  Rough   --   --   --   --   --                    100  --   -10 mesh                                                                             25    Weak   Rough   28   22   24   40   Melted                100  --   -10 mesh                                                                             30    Wet mass                                                                              Rough   --   --   --   --   --                    80   20** -10 mesh                                                                             20    Powdery                                                                               Rough   --   --   --   --   --                    80   20** -10 mesh                                                                             25    Good   Rough   38   21   18   59   No Sample             80   20** -10 mesh                                                                             30    Wet mass                                                                              Rough   --   --   --   --   --                    80   20***                                                                               -10 mesh                                                                             25    Powdery                                                                               Rough   --   --   --   --   --                    80   20***                                                                               -10 mesh                                                                             30    Powdery                                                                               Rough   --   --   --   --   --Best                80   20***                                                                               -10 mesh                                                                             35    Plastic                                                                               Rough   52   29   24   43   91                    100  --   -30 mesh                                                                             20    Too dry                                                                               Acceptable                                                                             --   --   --   --   --                    100  --   -30 mesh                                                                             25    Good   Acceptable                                                                             30   33   30   57   Melted                100  --   -30 mesh                                                                             30    Wet mass                                                                              Acceptable                                                                             --   --   --   --   --                    100  --   -30 mesh                                                                             35    Far too wet                                                                           Acceptable                                                                             --   --   --   --   --                    80   20***                                                                               -30 mesh                                                                             25    Powdery                                                                               Good    --   --   --   --   --                    80   20***                                                                               -30 mesh                                                                             30    Powdery                                                                               Good    --   --   --   --   --                    80   20***                                                                               -30 mesh                                                                             35    Good   Good    59   29   39   73   90                    100  --   -100 mesh                                                                            30    Powdery                                                                               Very good                                                                              --   --   --   --   --                    100  --   -100 mesh                                                                            35    Good   Very good                                                                              40   37   40   58   Melted                100  --   -100 mesh                                                                            40    Wet mass                                                                              Very good                                                                              --   --   --   --   --                    80   20***                                                                               -100 mesh                                                                            30    Powdery                                                                               Bast -- --   --   --   --                         80   20***                                                                               -100 mesh                                                                            35    Good   Best    76   60   63   89   104                   80   20***                                                                               -100 mesh                                                                            40    Wet mass                                                                              Best    --   --   --   --   --                    __________________________________________________________________________      *Moisture content determined on a dry weight basis                             **Initial sample of FBC fly ash                                                ***Second sample of FBC fly ash                                                ****Average of five 3/8 square inch specimens                            

In accordance with another aspect of the invention, concrete masonry units may be produced comprising varied proportions of FBCR, aggregate, fly ash, and cement. In this respect, it has been found that the following percentages by weight of the various components (based on the dry mix weight) have been useful: 25-60 weight % aggregate, 5-12 weight % fly ash, 25-60% FBCR, and 3-10 weight % cement.

EXAMPLE 5

Eight trial batches of masonry block, the compositions of which are herein reported in Table XI were prepared and cured in a steam heated tunnel kiln for 24 hours at approximately 130° F. The block specimens were stored on trays which were placed in frames. The frames were placed in the kiln in the order in which the batches were prepared. After the initial kiln cure, the frames were removed from the kiln. Two days after molding, blocks from each batch were tested in accordance with ASTM C-140, and the testing was repeated at 12 days of age and at 30 days of age. Table X.I also indicates the compressive strength of the various masonry units produced in accordance with this example, as tested by ASTM C-140.

                                      TABLE XI                                     __________________________________________________________________________     MIX DESIGN AND TEST RESULTS FOR CONCRETE MASONRY UNITS                         COMPOSITION                                                                    (Pounds per Cubic Yard)                                                        Mix Designation  Control                                                                             Mix 1                                                                               Mix 2                                                                               Mix 3                                                                               Mix 4                                     __________________________________________________________________________     Portland Cement - Type 1                                                                        328  349  327  319  118                                       Limestone Screenings Aggregate                                                                  3635 2044 1918 933  2247                                      (3/8")                                                                         Fly Ash - National Mineral Corp.                                                                71   215  404  394  237                                       AFB Residue      0    1077 1010 1969 1185                                      Water            246  358  348  364  310                                       Total Weight per Cubic Yard                                                                     4279 4043 4008 3979 4097                                      Compressive Strength @ 30 Days                                                 Age              820psi                                                                              1070psi                                                                             1453psi                                                                             212psi                                                                              278psi                                    Dry Unit Weight @ 30 Days Age                                                                   130.7pcf                                                                            119.5pcf                                                                            131.3pcf                                                                            102.1pcf                                                                            106.8pcf                                  Absorption       8.1% 10.8%                                                                               6.9% 18.0%                                                                               15.8%                                     % Compaction (Based on                                                         theoretical dry unit weight)                                                                    87.5%                                                                               87.6%                                                                               96.8%                                                                               76.3%                                                                               76.2%                                     __________________________________________________________________________      NOTE:                                                                          The control mix and mix numbers 1 and 2 can be compared directly, but the      proportions of fine and coarse fractions in mix numbers 3 and 4 resulted       in low densities which, therefore, did not provide a satisfactory product      High initial temperatures of 101° F. and 104° F. after           molding may have also been a factor.                                     

It is to be noted that the masonry units, reef blocks, and other articles produced hereby may be used by themselves, or may be crushed into aggregates of various sizes. Due to the surprisingly high compressive strengths of the disclosed mixes, they can be successfully employed in load bearing situations wherein conventional concrete formulations are now used. The aggregates exhibit excellent dimensional stability, high structural strength, low permeability and non-leachability. Due to the low permeability and non-leachability characteristics of the produced aggregates, they may be readily stockpiled without causing environmental concern due to leaching and surface run-off as is the case in the stockpiling of many other industrial waste products. The thus formed aggregates are especially useful for combination in various concrete mixes, mortar mixes, road base material mixes and in landfill mixes. The aggregate may also be used as ballast in varied applications.

The term "limestone" as herein used refers to naturally occurring limestone or dolomite generally consisting of calcium carbonate or a mixture of calcium carbonate and magnesium carbonate. As further used, reference to the "hydration of lime" or to "hydrated lime" refers to calcium hydroxide (hydrated high calcium quicklime) or a mixture of calcium hydroxide and either magnesium oxide (dolomitic monohydrate) or magnesium hydroxide (dolomitic dihydrate).

Those skilled in the art may make certain modifications or substitutions to my invention without departing from the true spirit thereof. The appended claims are intended to cover all substitutions and equivalent modifications. 

I claim:
 1. Cementitious composition comprising:(a) the anhydrous spent residue from a fluidized combustion bed of the type wherein limestone particles are suspended in a dry condition in the presence of a carbonaceous fuel in a fluidized medium and wherein the carbonaceous fuel is ignited within said fluidized medium to capture therein substantial amounts of SO_(x) which is generated upon ignition of said carbonaceous fuel said residue containing coal ash which is substantially free of finely divided siliceous-alumina glass compounds, (b) water, and (c) pozzolanic materials.
 2. Aggregate composition comprising 10-90% by weight fluidized bed combustion residue as defined in claim 1 and 90-10% by weight pulverized coal combustion system fly ash.
 3. Aggregate composition as defined in claim 2 wherein about 10-50% by weight fly ash and about 90-50% by weight fluidized bed combustion residue are provided, the foregoing percentages adding up to 100%.
 4. Aggregate composition as recited in claim 2 wherein said aggregate exists as a pellet-like shape.
 5. Aggregate composition as defined in claim 4 further comprising a sodium silicate binder.
 6. Aggregate composition as defined in claim 4 wherein said aggregate has been sintered.
 7. Masonry block comprising 10-90% by weight fluidized bed combustion residue as defined in claim 1 and 90-10% by weight pulverized coal combustion system fly ash.
 8. Masonry block as recited in claim 7 wherein about 10-50% by weight fly ash and about 90-50% by weight fluidized bed combustion residue are provided, the foregoing percentages adding up to
 100. 9. Reef block comprising 10-90% by weight fluidized bed combustion residue as defined in claim 1 and 10-90% by weight pulverized coal combustion system fly ash.
 10. Reef block as defined in claim 2 wherein about 10-50% by weight fly ash and about 90-50% by weight residue are provided, the foregoing percentages adding up to
 100. 11. Concrete composition comprising:(a) fluidized bed combustion residue as defined herein in claim 1; (b) aggregate; (c) cement; (d) fly ash.
 12. Concrete composition as defined in claim 11 wherein about 25-60 weight percent aggregate, about 5-12 weight percent fly ash, about 25-60% fluidized bed combustion residue and about 3-10 weight percent of cement are provided, the foregoing percentages being based upon the dry weight of the concrete composition, and the foregoing percentages equaling
 100. 13. Cementitious composition as defined in claim 1 wherein the anhydrous spent fluidized combustion bed residue contains about 7 to about 20% carbonaceous fuel ash.
 14. Cementitious composition as defined in claim 1 wherein the anhydrous spent fluidized combustion bed residue has a loss on ignition of about 0.5 to about 15%.
 15. Cementitious composition comprising:(a) about 10-90% by weight of the anhydrous spent residue from a fluidized combustion bed of the type wherein limestone particles are suspended in a dry condition in the presence of a carbonaceous fuel in a fluidized medium and wherein the carbonaceous fuel is ignited within said fluidized medium to capture therein substantial amounts of SO_(x) which is generated upon ignition of said carbonaceous fuel, said residue containing coal ash which is substantially free of finely divided siliceous-alumina glass compounds, (b) water, and (c) about 90-10% by weight fly ash. 